1. Field of the Invention
The present invention relates to a magnetic recording and reproducing system and, more particularly, to an apparatus for detecting a tape terminus in a magnetic recording and reproducing system, by detecting a starting portion or an ending portion of a tape during recording and reproduction.
2. Description of the Related Art
In general, a magnetic recording and reproducing system for a cassette tape is provided with multiple guiding members and guide poles for guiding the tape supplied from a supply reel for the cassette tape, a head for recording and reproducing information, and a pinch roller and capstan axis for transferring a tape at a constant speed, along a travelling track of the tape. In order to prevent excessive tension from being applied to the tape during recording and reproduction, to protect the driving device thereof and to control the operation of the reproducing apparatus, there is also provided a detection means for detecting a starting portion or an ending portion of a tape. Here, the starting portion and the ending portion of the tape are generally made of a transparent material which is optically transmissible.
An example of such a detection means is disclosed in FIG. 1. A light emitting device 21 is installed between a supply reel 11 and a take-up reel 12, light receiving devices 22 are installed on opposite sides of the light emitting device 21, and a travelling cassette tape is positioned between the light emitting device 21 and each of the light receiving devices 22.
In the conventional detecting means having the aforementioned configuration, when the light emitting device 21 and the light receiving devices 22 operate, the cassette tape 100 is wound on the take-up reel 12 via the guiding member and the head during recording and reproducing. In the course thereof, if the optically transmissible starting portion or ending portion of the tape 100 positioned at either terminus of the tape 100 starts to unwind, the light radiated from light emitting device 21 passes through the transparent portion (starting or ending terminus), so as to be detected by the corresponding light receiving device 22, thereby detecting the starting portion or the ending portion of the tape 100. Once the light is detected by either of the light receiving devices 22 as described above, the operation of stopping and/or rewinding the tape 100 is performed by a microprocessor provided in the magnetic recording and reproducing system.
However, since the light emitting device 21 and the light receiving devices 22 should be fixed on a deck by means of separate members, for the conventional detection means as above, the configuration thereof becomes complicated. Also, if the relative positioning of the light emitting device 21 and the light receiving devices 22 becomes skewed, the operations thereof cannot be performed properly.
A conventional detecting means for solving such a problem is disclosed in Japanese Laid-open Patent Publication sho 63-4450. Referring to FIGS. 2 and 3, the detecting means includes a light receiving/emitting device 30 having a light emitting portion 31 which is light-emissive bidirectionally, and a light receiving portion 32 which is light-receivable bidirectionally. Light receiving/emitting device 30 is internally installed between the tape. The detecting means further includes two optically reflecting members 40 installed opposingly on either side thereof.
According to the conventional tape detecting means having the above-described configuration, the light emitted from light emitting portion 31 of light receiving/emitting device 30 is reflected onto reflecting members 40 installed outside the tape and is detected in light receiving portion 32 of the light receiving/emitting device 30, thereby detecting the starting or ending portion of the tape.
Such conventional detecting means reduce the manufacturing cost by installing only a single light receiving/emitting device 30 having a light emitting portion 31 and a light receiving portion 32. However, since the detection is performed such that the light emitted from light emitting portion 31 is reflected onto reflecting members 40 and then is detected in receiving portion 32, it is important to prevent any obstructions along the light path between light receiving/emitting device 30 and reflecting members 40. Therefore, it is quite difficult to install such a detecting means sufficing the aforementioned requirement.